Heteroepitaxy of Highly Oriented GaN Films on Non‐Single Crystal Substrates Using a Si(111) Template Layer Formed by Aluminum‐Induced Crystallization

Abstract

Growth of epitaxial III‐nitride (AlGaInN) films has long been confined to single crystal substrates which are crystallographically compatible with the hexagonal GaN (0001) surface. However, for lighting, display, and power electronics applications, growth on amorphous substrates such as fused quartz glass or on polycrystalline diamond is desirable. Several approaches to produce c‐plane oriented, textured GaN films on glass have been previously demonstrated, but are process‐intensive and limited in scalability. In this report, we demonstrate the heteroepitaxial growth of textured GaN films on fused quartz and other substrates using thin silicon film templates fabricated by aluminum‐induced crystallization (AIC). The AIC‐Si films have a uniform (>95%) Si (111) oriented surface, enabling well‐developed GaN‐on‐Si epitaxial growth processes to be adapted to new substrates. GaN films grown on fused quartz using metalorganic chemical vapor deposition (MOCVD) have uniformly c‐axis oriented grains, ≈40–50 μm in size, with random in‐plane orientations similar to those of the underlying AIC‐Si template layer. Threading dislocation densities of 8.5 ± 1.8 × 109 cm−2 within regions bounded by grain boundaries are comparable to GaN films grown on single crystal Si (111) substrates. Finally, highly oriented GaN growth on AIC‐Si is also achieved on both oxidized Si (001) substrates and polycrystalline diamond, demonstrating the general applicability of this approach.

Pole figure analysis from electron backscatter diffraction—an effective method of evaluating fiber-textured silicon thin films as seed layers for epitaxy

“…In comparison, the GaN film grown on the uniformly oriented seed layer was visibly smoother and more coalesced, with greatly reduced tilt. In fact, the FWHM for this peak was roughly half of the previous reported FWHM for GaN growth on AIC-Si seed layers 17). These results demonstrate how seed layer misorientation effects subsequent heteroepitaxial film quality, and provides a method for selecting high-quality seed layers.…”

“…In fact, the FWHM for this peak was roughly half of the previous reported FWHM for GaN growth on AIC-Si seed layers. 17) These results demonstrate how seed layer misorientation effects subsequent heteroepitaxial film quality, and provides a method for selecting high-quality seed layers. Furthermore, by using AIC-Si seed layers with known misorientations, GaN growth conditions can be studied independent from the Si seed layer, allowing for the effects of GaN growth conditions on GaN on AIC-Si heteroepitaxy to observed.…”

“…Of particular interest is the ultra-thin (t < 50 nm) film regime, where Si films can be fabricated with greater than 95% (111) surface orientation, [8][9][10] potentially allowing well-developed processes for growth on Si(111), Ge(111), and similar surfaces to be adapted to new substrates. Previously, homoand heteroepitaxy of Si, Ge, and GaAs nanowires, 11,12) Si [13][14][15][16] and Ge 7) thin films, and GaN 17) have been demonstrated on AIC-fabricated Group IV seed layers.…”

“…4. GaN heteroepitaxy on Si seed layers fabricated by AIC has been previously demonstrated, 17) but because Si seed layer quality and GaN growth conditions were difficult to characterize independently, the factors determining final GaN film quality could not be clearly determined. Pole figure analysis allows for characterization of the Si seed layer separately from the GaN film, and as seen in Fig.…”

“…As such, the uniform surface orientation and reduced misalignment relative to the 〈111〉 direction makes the film characterized in Figs.3(c)-3(d) more suitable to subsequent heteroepitaxial applications than the one in Figs.3(a)-3(b).The effect of seed layer misorientation on subsequent heteroepitaxy can be seen in Fig.4. GaN heteroepitaxy on Si seed layers fabricated by AIC has been previously demonstrated,17) but because Si seed layer quality and GaN growth conditions were difficult to characterize independently, the factors determining final GaN film quality could not be clearly determined. Pole figure analysis allows for characterization of the Si seed layer separately from the GaN film, and as seen in Fig.4, samples grown with either misoriented (blue) or uniformly oriented (red) Si seed layers in the same growth run under identical reactor conditions produced significantly different GaN thin films.…”